1. Field of the Invention
The present invention relates to an image processing apparatus and a control method therefor.
2. Description of the Related Art
To comply with energy-saving standards which have been becoming more and more strict, image forming apparatuses, such as printers, facsimile machines, digital copying machines, and digital multifunction machines, power supply to some component parts of the apparatus is shut down during standby to thereby largely reduce power consumption.
For example, in the case of an image forming apparatus of the type in which print data supplied from an external device, such as a personal computer, is expanded into bit data, which is supplied to a laser printer, interruption of energization of a fixing unit of the laser printer, stoppage of driving of a cooling fan, shutdown of power supply to a CPU, and so forth are carried out when the apparatus is in a power saving mode.
On the other hand, an image forming apparatuses designed to operate on a network is desired to be capable of recovering a normal operation mode from a power saving mode at high speed, when required.
Further, in recent digital multifunction machines, the programs for controlling the operation of the machine have increased in size, so that if all the programs are to be stored in a ROM, there is a fear of an increase in cost. To eliminate this inconvenience, some of the programs are stored in an area of a hard disk for storing images (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. H06-067770).
In such an apparatus that stores programs in an area of a hard disk thereof, however, after the apparatus is started, the programs are once downloaded from the hard disk into a RAM, and then the CPU reads the programs from the RAM to execute the same, which makes it impossible to comply with the requirement of high-speed recovery of the normal operation mode.
As a solution to this problem, an apparatus has also been proposed which uses a sub CPU for use in a standby mode for saving energy. Under the recent situations in which competition for cost reduction has become intensified, it is not practical to provide a low-price apparatus with such a sub CPU.